9 folders cost $9.45. Which equation would help determine the cost of 14 folders?
Answer: There are several equations that could help determine the cost, each with a slightly different approach. We can write the fact that 9 folders cost $9.45 as a proportion: $\dfrac{9}{\$9.45}$ Let $x$ represent the unknown cost of 14 folders. Since 14 folders cost $x$ , we have the following proportion: $\dfrac{14}{x}$ The cost changes along with the number of folders purchased, and so the two proportions are equivalent. $\dfrac{9}{\$9.45} = \dfrac{14}{x}$